1. Field of the Invention
The present invention relates to piezoelectric ceramic compositions and piezoelectric ceramic devices using the same. In particular, the present invention relates to piezoelectric ceramic compositions, which are useful as materials for piezoelectric ceramic filters, piezoclectric ceramic oscillators and piezoelectric ceramic vibrators, and relates to piezoelectric ceramic devices using the same.
2. Description of the Related Art
Piezoelectric ceramic compositions comprising lead titanate zirconate (Pb(Ti.sub.x Zr.sub.1-x)O.sub.3) or lead titanate (PbTiO.sub.3) as main components are extensively used in piezoclectric ceramic filters, piezoelectric ceramic oscillators, and piezoelectric ceramic vibrators. In piezoelectric ceramic compositions comprising lead titanate zirconate or lead titanate as the main components, lead oxide is generally used. Lead oxide, however, requires facilities such as filters for removing powdered lead oxide, which is scattered by vaporization during the production steps. Such facilities incur increased production costs. In addition, the vaporization of the lead oxide causes deterioration of the uniformity of product quality.
On the other hand, piezoelectric ceramic compositions comprising bismuth layered compounds such as (Sr.sub.1-x M.sub.x)Bi.sub.2 Nb.sub.2 O.sub.9 as main components and Mn as an optional component do not contain lead oxide and do not cause the above problems. These piezoelectric ceramic compositions, however, must be sintered at high temperatures of at least 1,250.degree. C. in order to obtain piezoelectric ceramics having electromechanical coupling coefficients kt of at least 10%, which are at practical levels. Thus, these piezoelectric ceramic compositions require sintering furnaces which withstand such high-temperature sintering. Moreover, setters and the like for containing the piezoelectric ceramic compositions during sintering have short service lives in high-temperature operation, resulting in increased production costs.